(() => {
    // 基础类型
    let flag: boolean = true
    console.log(flag);

    let num: number = 110
    console.log(num);

    let str: string = '周张恒'
    console.log(str);

    let any: any;

    console.log('===================');


    // undefined和 null
    let und: undefined = undefined
    let nll: null = null
    num = undefined
    console.log(und, nll, num);

    console.log('===================');

    // 数组类型
    let arr1: number[]
    let arr2: Array<object>
})()